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Ethical issues raised by

genetically modified microorganisms Michel Gautier, Laboratory of Microbiology and Food Hygiene, UMR STLO 1253,

Agrocampus, 65 rue de Saint Brieuc, 35042 RENNES CEDEX

(N.B.: all terms marked with an asterisk feature in the glossary at the end) Unlike experiments carried out on humans and animals, applications involving

microorganisms and their genetic modification do not cause pain and suffering as generally

understood. The ethical problems raised by genetically modified microorganisms (GMMs)

therefore mainly related to the impact they have on the Earth's biosphere. As microorganisms

can be found everywhere, including in the ecological niches that are the most unsuited to life

forms, the repercussions can be substantial and irreversible.

.

In order to clearly grasp to what extent GMMs can be dangerous for humans and their

environment, it is necessary, on the one hand, to define them and explain the context in which

they are used or can be potentially used (this will be the subject of the first part of this text)

and on the other hand, to specify the possible risks of these uses (this will be the subject of the

second part). Next, having put these risks in perspective in the third part, we shall question the

actual usefulness of these GMMs (can we do without them or not?) as, in the end, given the

lack of knowledge currently available, the most effective way of solving this ethical problem

once and for all is perhaps to reduce their use. We will end with the role of researchers in the

emergence of these new organisms that they cannot yet completely control.

1. What is a genetically modified organism?

1.1. Which microorganisms are concerned?

In a phylogenetic* tree featuring all living organisms, the majority of these (in terms of

diversity) are microorganisms: one branch of this tree includes true bacteria (also known as

eubacteria) whereas the other two branches consist of archaebacteria and eukaryotic*

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microorganisms. These notably include protozoa, unicellular algae, and yeasts and moulds

(Bapteste et al., 2004).

Within these three main categories of microorganisms, it is bacteria that have undergone the

most genetic modification. However, within the eukaryotes, we do find moulds and yeasts

that have also undergone genetic modification, although this is rarer.

This text will not cover the problem of viruses which, as they are not autonomous and require

another organism to multiply, need to be studied separately.

1.2. What is a genetically modified organism?

A microorganism is considered to be genetically modified if:

- genetic material has been inserted into it by an unnatural method, i.e. other than

natural conjugation, transformation or transduction.

- genetic material that has been modified in vitro has been inserted into it. In this case,

even if a natural transfer method has been used, the microorganism is still considered

to be genetically modified.

The gene that has been inserted into the bacteria can be homologous, i.e. it comes from the

same species, or heterologous, in which case it has come from another species or bacterial

genus (e.g. cloning of a Bacillus thuringiensis gene encoding an insecticide in Pseudomonas)

(Wilson and Lindow, 1993). A heterologous gene can also come from an animal or plant cell

(e.g. cloning the gene encoding human insulin in Escherichia coli).

DNA modified in vitro (foreign DNA) can be:

- either inserted into a cloning vector, i.e. a set of genes capable of enabling the genes

that have been transferred to the bacteria to replicate in it; in this case the foreign

DNA includes the cloned gene and the often heterologous genes making up the

cloning vector.

- or inserted into the chromosome; in this case the foreign DNA is generally exclusively

made up of the cloned gene.

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1.3. In what cases can microorganisms and (a fortiori) genetically modified

microorganisms be used? Are they useful?

There are five categories in which microorganisms — including or potentially including

GMOs — can be used.

a) for producing molecules or biomass in a fermenter,

b) for producing fermented foods,

c) for various uses in the environment (in agriculture, for pollution control, etc.),

d) for producing strains for therapeutic purposes (e.g. live vaccines),

e) for gaining fundamental knowledge.

With certain technologies, living microorganisms can be released into the environment where

they may multiply. To guard against this risk, many countries have legislated against these

GM technologies.

1.3.1. Using microorganisms in a fermenter

Since the mid-20th century, microorganisms have been widely used to produce numerous

molecules required by the pharmaceutical, agri-food and chemical industries. Moreover, they

are produced in fermenters to develop the starter cultures required by the fermented food

industry.

In the pharmaceutical industry, many molecules (such as antibiotics or vitamin B12, for

instance) are produced by microorganisms which synthesise them naturally. There are also the

even more numerous molecules whose gene has been cloned in a microorganism (e.g. human

insulin, growth hormone, Hepatitis B vaccine). All these molecules have been marketed for

many years and are part of developed countries' daily therapeutic arsenal (recombinant insulin

has been produced since 1983) (Swartz, 2001).

In the agri-food industry, intermediate products such as enzymes* (e.g. amylases, rennin),

amino acids*, organic acids and even nucleic acids* are produced by microorganisms. In the

same way as above, these molecules can be naturally synthesised by microorganisms or come

from GMMs.

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Lastly, the chemical industry features many molecules (such as enzymes, organic acids and

biofuels) produced by microorganisms.

Producing molecules in a fermenter involves culturing the microorganism responsible for

producing the required molecule in a (generally) confined space containing a suitable nutritive

medium. This operation is generally performed in a confined atmosphere and, in theory, does

not cause microorganisms to be released into the environment. It must meet Community

requirements (European directives 90/219 and 98/81). In order to master the technology,

many GMM culture approvals have been granted over the past few decades (European

directive 2001/18/EC). In theory, they are only granted once the risks to public health and the

environment have been fully assessed.

There is little diversity in microbial species that are genetically modified to produce useful

molecules, as they are often model microorganisms that have been studied over a long period

and for which the recombinant DNA technologies are very sophisticated and well-known.

They include mainly bacteria (e.g. E. coli (Baneyx, 1999), Bacillus subtilis) and yeasts

(notably Saccharomyces cerevisiae) (Ostergaard et al., 2000).

1.3.2. Producing fermented foods

Microorganisms are the main agents in the production of vast numbers of fermented

foodstuffs. In Europe, many GMM strains used in this process have been available in research

laboratories for a long time but are not yet used for legal reasons, unlike in the U.S.A.

Bread, wine, cheese, butter, creme fraiche, yoghurts, kefir, fermented meats (dry-cured

sausage, salami) and fermented vegetables (sauerkraut, olives) are produced by the action of

an extremely varied microbial flora. Some fermented foods are produced from a complex and

little known microbial flora (that may be categorised as wild flora) found in raw materials and

the environment (some unpasteurised cheeses, beers and sourdough bread); others are made

from industrial starter cultures of simpler composition and identified flora (many cheeses

made from pasteurised milk, for example) and lastly other fermented foodstuffs contain both

complex wild flora and industrial flora, which has been added deliberately and in controlled

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conditions (this is notably the case of fermented foodstuffs whose raw material cannot be

sterilised, such as dry-cured sausage, etc.).

Whatever the case, apart from the majority of fermented drinks and bread, at the end of

fermentation fermented foods generally contain roughly 109 microorganisms/gram.

Depending on the type of food, this flora may or may not be living when the food is ingested

by the consumer. Microbial flora then travels through the digestive tract and does not

generally stay there, consequently ending up in the environment through faeces.

Why use GMOs for fermented foods?

Foods with complex flora are useful due to their elaborate organoleptic properties, but they

can be the seat of pathogenic microorganism development. In addition, their production is

difficult to control as microbial flora fluctuates according to the environmental conditions. On

the other hand, foods with controlled flora are less useful from an organoleptic viewpoint but

safer.

For several years, in order to produce fermented products with controlled flora that are as

advantageous from an organoleptic* viewpoint as wild flora-derived foods, industrialists have

added new bacterial species isolated from wild flora-derived foods to their starter cultures.

But until very recently, they were unable to guarantee that these new species were totally

harmless, which thus raised doubts about the safety of these foods. The use of GMMs to

produce fermented foods would, on the one hand, solve the problem related to the use of

little-known flora and, on the other hand, overcome the various technological problems thanks

to the development of improved strains.

The use of GMMs to produce fermented foods is highly regulated, at least in the European

Union. The presence of living microorganisms in foods ingested by humans is hampering the

use of GMMs. Be that as it may, many bacterial strains and improved yeasts (in terms of

industrial properties) are available in the research laboratories of numerous international

teams.

1.3.3. Using microorganisms for various applications in the environment (in agriculture,

pollution control, etc.)

Microorganisms come into play in many pollution control processes, the most common of

which is sewage treatment, a process that involves highly complex wild flora. Methods for

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controlling pollution of more specific compounds (hydrocarbons, slurry, various pesticides,

etc.) have also been developed and involve selected flora, which is less complex (in terms of

diversity). However, the action of this flora is far from optimal and therefore requires genetic

improvement. Numerous microbial GMOs with properties that are compatible with the

process (resistance to the substrate to be biodegraded, good establishment in the environment,

etc.) have been developed in laboratories but they cannot be used for legal reasons, as there is

a risk of uncontrolled dispersal into the environment.

Lastly, in agriculture, microbial strains are used to enhance the growth of plants and crop

protection. In the same way as above, it has been necessary to develop genetically

recombinant strains to optimise the processes. The use of these strains in the environment is

currently banned in Europe but has been authorised in the United States for several years.

Strains of Sinorhizobium meliloti that have been genetically improved to enable nitrogen

fixation by the plant have been used since 1997 to seed legume crops.

Similarly, pesticides (Nogall and Mattch) using other genetically improved species

(Agrobacterium radiobacter) are used in soils.

1.3.4. Production of strains for therapeutic purposes

Owing to their ability to survive or pass through human and animal mucosa, microorganisms

can be used to treat or prevent certain diseases. For example, a strain of Lactobacillus jensenii

has been modified to secrete the CD4 protein used by the HIV virus in the vaginal mucosa to

penetrate lymphocytes. This secreted protein also traps viruses (Chang et al., 2003). Even if

these GMMs can solve major therapeutic problems, they are not always used because of their

potential dispersal into the environment.

1.3.5. Use of microorganisms in laboratories to gain fundamental knowledge

Another no less important use of genetically modified microorganisms is in research

laboratories, as they enable us to better understand how microorganisms function. Numerous

genes belonging to a wide variety of microbial species have therefore been cloned and have

given rise to thousands of GMM strains used as research material by researchers.

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In short, in the Europe of today, genetically modified microorganisms are mainly used to

produce molecules in fermenters. In this case, the microorganisms are in fact maintained in a

confined atmosphere which theoretically prevents their release into the natural environment.

They are used to produce the molecules used in the pharmaceutical, agri-food and chemical

industries.

In the United States, the situation is somewhat different as some GMM strains are used to

produce fermented foods and, more generally, in environmental processes.

2. What are the risks posed by genetically modified microorganisms?

The unicellular nature and relative simplicity of microorganisms means that they are able to

multiply very rapidly: Escherichia coli is therefore able to give birth to two new cells in 20

minutes when it is cultured in an optimum culture medium. In the same way, Lactococcus

lactis divides in 30 minutes when it is cultured in milk for the production of soft cheeses.

This property, together with their extremely small size which means that they are able to be

dispersed efficiently into the environment by wind and water, allows microorganisms to reach

a great variety of potential ecological niches.

The ease with which they are able to colonise these ecological niches allows microorganisms

to adapt to a wide variety of environments which may pose difficulties for any other living

organism. These bacteria demonstrate an extreme genetic adaptability due, on the one hand, to

the fact that they are haploid (they only contain one chromosome, meaning that any mutation*

is clearly expressed) and, on the other hand, to the fact that they may acquire genes from other

microorganisms (horizontal transfers).

These mutations and acquisitions of new genes give rise to the appearance of a large number

of microbial variants which are selected through pressure from the natural environment if the

characteristics that they have acquired allow them to adapt more successfully to this

environment.

The danger posed by these genetically modified organisms is therefore related both to their

dispersal into the environment and to their potential for adaptation to a new environment. In

so doing their development may, by altering the animal and plant microbial ecological

balance, disrupt this environment to a greater or lesser extent. If, however, they are unable to

develop in this environment, they may potentially transfer their modified genetic material to

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other microorganisms, thus leading to the appearance of new variants which, themselves, may

have the capability of greatly disrupting this environment.

2.1. What might happen when a genetically modified microorganism is released into the

environment?

2.1.1. Possibilities of gene transfers to other organisms

Microorganisms are capable of acquiring new genes from other living microorganisms or

microbial corpses in the natural environment. In the latter case, the free DNA in the

environment is often damaged, although some habitats, such as marine sediments, limit this

damage.

There are three main types of mechanism for gene transfer between microorganisms:

conjugation, transformation and transduction.

Conjugation is a form of gene transfer between two bacterial cells. Certain genes, known as

“transfer genes”, bring cells closer together and, through the formation of a cytoplasmic

bridge*, allow DNA to travel between the two bacteria (one of the bacteria therefore becomes

known as the “donor” and the other the “recipient”). In general, transfer genes are carried by

plasmids (small loops of DNA which are capable of replication independently of the

chromosome) which replicate both in the donor and the recipient bacteria. These plasmids do

not only contain transfer genes but also other genes which often allow the bacteria to adapt to

an ecological niche (genes encoding numerous resistance mechanisms or allowing the

assimilation of nutritional elements, for example). This means that bacteria having acquired a

plasmid by conjugation may, in turn, transfer it, thereby acquiring new properties. However,

these plasmids (known as conjugative plasmids) are not able to be transferred to all bacterial

species. There is a host specificity, meaning that some plasmids are able to replicate and be

expressed in species which are very varied from a phylogenetic point of view, while others

have a narrow host spectrum which only allows them to replicate and be expressed in a small

number of species, or even just within a single bacterial species. In a way, this host spectrum

controls and limits conjugative transfer in the bacterial world. In the case of GMMs, some

genetic improvements are relatively frequently encoded and carried by a plasmid (known in

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this case as a cloning vector). In order to limit gene transfers, these vectors do not carry

transfer genes. Nevertheless, it is possible that they may be transferred to other bacteria if they

are accompanied by a conjugative plasmid. During conjugation, plasmids which do not

possess transfer genes may benefit from the enzymatic machinery established by the

conjugative plasmid in order to cross into the recipient bacteria at the same time as the

conjugative plasmid. However, vectors which are transferred in this way must then be capable

of replicating and being expressed in the recipient bacteria.

Transformation is a mechanism which allows some bacteria to acquire exogenous DNA

(DNA from dead and lysated cells which circulates freely in the natural environment) and to

integrate it into its genome. This mechanism, which has been very well described for some

bacterial species, allows bacteria to repair their genome when it is damaged (by exchanging

damaged genes with others from dead bacteria) and also to acquire new genes from other

bacteria. In the same way as above, this mechanism does not allow bacteria to acquire just any

type of gene. The DNA which penetrates the bacteria must be able to be incorporated into the

genome and must therefore have a certain sequence homology in order to allow

recombination* with the chromosome. Moreover, this mechanism may be more or less

effective depending on the species and it is not yet known whether all species possess this

mechanism or one of a similar nature.

Transduction is the transfer of bacterial DNA to other bacteria by a bacteriophage, a virus

specific to bacteria. When bacteria is infected by a bacteriophage, an event which occurs

frequently in nature, this virus, when it multiplies in the bacterial cell, carries with it bacterial

DNA instead of phagic DNA. When it reinfects new bacteria, it therefore injects it with this

bacterial DNA. If it is plasmid DNA, it may potentially be able to survive in the bacteria. If it

is chromosomal DNA, it may potentially become incorporated into the chromosome insofar as

it is sufficiently homologous for a recombination to occur. For bacterial GMOs, the transfer of

modified DNA may well take place by transduction; the capacity of the cloning vector to

replicate in the recipient bacteria depends on its host spectrum and, in the case of

chromosomal DNA, the ability to incorporate into the chromosome depends on the degree of

homology with the DNA of the recipient bacteria.

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These gene transfer mechanisms may allow a diverse flora to acquire new properties. This

means that a genetically modified microorganism has the potential to transfer, whether dead

or alive, genes which have been modified in laboratories.

The unregulated acquisition of new genes by microorganisms may potentially lead to the

appearance of new pathogenic germs (for example through the acquisition of genes involved

in virulence or in the colonisation of a new organism). These gene transfers may also lead to

unwanted biochemical reactions which may have an impact on the environment (damaging

important plant compounds, for example), or to the production of toxic compounds.

It is also conceivable that these gene transfers may lead to the emergence of new microbial

variants which may acquire properties allowing them to colonise a new ecological niche and

to replace the endogenous population, thus disrupting the microbial balance.

Although gene transfers between microorganisms are frequent and these mechanisms are

partially identified, they are nevertheless a cause for concern in the case of GMMs. For

example, researchers have shown that gene transfers between Agrobacterium tumefaciens

(Demaneche et al., 2001), the bacteria used to modify the genes of plant species, and

Pseudomonas fluorescens most likely occur naturally in soils. Gene transfers between

microorganisms and so-called “superior” organisms are less well-known, but nonetheless

probably take place. Researchers have observed such transfers, for example, between a

bacterium (Wolbachia sp) and an insect (Callosobruchus chinensis) (Kondo et al., 2002).

2.1.2. The development of new microorganisms in the environment

Genetically modified microorganisms are often designed for a specific function. Nevertheless,

we do not have sufficient knowledge of the microbial metabolic pathways in order to have

complete control over the appearance of new properties resulting from the modification of

genes in laboratories. If unforeseen metabolic modifications can occur in a microorganism

whose genome has been modified, it is also highly likely that they can occur in other species

in the environment which have acquired these modified genes through horizontal transfer.

It should be remembered at this stage that microorganisms exist in huge numbers in the

environment (for example, there are at least 109 microorganisms per gramme in fertile humus,

105 per millilitre in the water of a river running through a town and 109 per millilitre at the

outlet of a sewage treatment plant) and they are represented by a large number of diverse

species (there are several hundred in the digestive tract of mammals, for example, or in the

anaerobic reactor of a sewage treatment plant). The possibilities for gene transfers between

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these microorganisms in a given ecosystem are therefore numerous and may lead to the

emergence of more adapted variants.

If these new properties give a selective advantage to a species, it is possible that this species,

being better adapted to a new environment, may colonise it, thus greatly disrupting the

ecological balance, whether microbial, plant or animal. Such a problem is genuinely

conceivable and was apparent even before the arrival of GMMs: some cases are already

known in which microorganisms have found themselves in a new ecological niche as a result

of (generally accidental) human intervention. They have subsequently colonised this niche,

disrupting it to a great extent. A well-known example of this involves the toxigenic*

unicellular alga Chrysochromulina polylepis (Belsher et al., 2003) which, because of human

activity (the release of nitrogenous substances into the sea), invaded part of the North Sea and

the English Channel, leading to significant health problems as it produces toxins which are

pathogenic for humans. Even though not a microorganism, this is also the case of the alga

Caulerpa taxifolia (Belsher et al., 2003) which, probably as a result of the accidental

emptying of the aquariums of the Oceanographic Museum in Monaco, is currently colonising

the Mediterranean sea bed and causing the death of the endogenous fauna.

2.1.3. Multiplication of pathogenic microorganisms

Research into pathogenic microorganisms requires, among other things, the cloning of genes

encoding the pathogenicity factors in other microbial species, thereby giving rise to genetic

events which would probably not naturally have taken place, and therefore the appearance of

strains representing a new pathogenic power. Even though these laboratory experiments,

concerning plant, animal and human sectors, do not directly aim to create strains which are

more pathogenic but to aid the understanding of pathogenicity mechanisms, our current level

of knowledge means that we are not able to ensure the complete harmlessness of these

transgenic microorganisms. Thus US researchers, by inhibiting the activity of a virulence

gene in Mycobacterium tuberculosis, created a variant which was much more virulent than the

native strain (Shimono, 2003). The issue is even more crucial when it comes to the

development of biological weapons: in this case, the primary objective is the creation of new

pathogens against which an army or an enemy country is not able to defend itself. A US team

thus recently modified the smallpox virus so that it would bypass the immune defences in

humans due to vaccination or be resistant to available drugs. Another area of research

involved the modification of the cowpox virus so that it might cross species barriers and infect

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other species, such as humans. One of the viruses developed demonstrated an increased

pathogenicity (New Scientist, 2003). Such GMOs threaten to escape the control of scientists

and to have unpredictable consequences on animal and human species.

3. Things must be put into perspective

3.1 Genetic modifications of microorganisms also occur naturally

Nature does not need humans in order to modify the genetic inheritance of microorganisms.

Their extremely short generation time (compared with that of superior beings such as

animals), which allows them to reach a very high population size in a short space of time,

means that microbial populations continuously generate a large number of mutants. A mutant

may be defined as an individual which has a different genetic inheritance from that of its

parents without having acquired new genes by horizontal transfer. A mutation may be a one-

off variation in a nucleotide base within a genome or a genetic rearrangement (gene inversion,

loss or duplication).

The phenomena which lead to mutations may be natural or caused by external agents of the

natural environment. Some bases which make up genes may thus naturally change and be

transformed into other bases. Elements from the external environment, such as radiation

(ultraviolet rays, for example) or chemical molecules resulting from human activity or the

activity of other organisms — including microorganisms — may be responsible for these

mutations.

Such mutations are actually due to lesions in the genetic material which, if poorly repaired,

give rise to a change in genetic information. The environment will then carry out a process of

selection, allowing the emergence of the best adapted mutants. Consequently, when someone

suffering from a bacterial infection is treated with an antibiotic, the use of the antibiotic may

inadvertently lead to the selection of mutants which are resistant to it. These few mutants

which are resistant to the antibiotic, and which constitute just a small proportion of the

infecting bacterial population, will thus survive and replace all the original population.

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This appearance of mutants with new properties is a phenomenon which has been well known

for some time. Spontaneous yeast mutants have thus been used in brewing techniques for

several decades.

As it is a natural and commonplace occurrence, mutagenesis is frequently used to improve the

properties of microorganisms in all sectors where they are used (the pharmaceutical and food-

processing industries, farming, pollution control, etc.). Strains modified in this way may be

used and then released (or used) in the environment without posing any problems, ethical or

otherwise.

The extreme diversity of microbial species and the large populations mean that genetic

transfers between individuals are likely to be considerable in nature, thus contributing greatly

to microorganisms’ exceptional capacity for adaptation to environmental variations. If

humans are able to carry out genetic modifications of microorganisms by the introduction of

new genes, it should be remembered that this process also occurs naturally in the

environment.

3.2. Recombinant microorganisms are not well adapted to the environment

During their time in vitro, “laboratory creatures” have a tendency to lose their capacity to

colonise an environment or even to survive in their natural habitat. Several experiments have

demonstrated that once the model strains which are used in laboratories (Escherichia coli,

Saccharomices cerivisae, Bacillus subtilis, etc.) are removed from their test tubes, they have

very little chance of surviving in their natural habitat. Successive culture on rich or selective

media of these model strains used in laboratories, or genetic modifications carried out by

researchers, mean that they have long since lost some of the faculties which are necessary for

their adaptation to a complex environment colonised by a diverse flora. This observation does

not just concern model species as, even when a strain taken from the natural environment and

thus adapted to a complex flora is isolated and is cultivated for just a short time in a

laboratory, it rapidly loses the faculties which allow it to settle back into the environment

from which it comes. Nevertheless, these microorganisms, even if unable to survive in their

natural habitat, are able, on their death and subsequent cellular lysis, to release DNA which

may be captured by other microorganisms.

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3.3. Gene transfers are limited

The process of gene transfer between microorganisms as described above does not allow gene

flow between all species: some transfers may be limited to certain strains within a species,

others take place between closely-related species or, more rarely, between phylogenetically

distant species, and a small number occur between different bacterial genera. If a total mixing

of genes seems impossible, this is because there are several genetic mechanisms which limit

gene transfers. In the event of a GMM being released into the environment, these mechanisms

therefore restrict the spread of modified genes to wild flora.

For example, transduction does not generally allow DNA transfers between very different

species. The infection mechanisms of bacteriophages are specific to each strain. This means

that, in general, bacteriophages are only able to infect strains of the same species, even if

certain, quite rare, bacteriophages can cross species barriers. In the same way, for some

species, the natural transformation of bacteria (foreign DNA from the external environment

crosses the barrier into the bacterial cytoplasm) requires the presence of specific sequences on

the exogenous genome. Some bacteria are therefore only able to acquire DNA comprising

these particular sequences, which are often species-specific.

Finally, there are various bacterial mechanisms which are capable of damaging foreign DNA

which enters into the bacteria (restriction-modification systems and the SMR system), making

the bacteria unable to incorporate the foreign DNA.

In the same way, some genes are only able to express themselves in a certain type of bacteria.

For example, it is known that the genes of Gram-positive* bacteria express themselves

relatively easily in Gram-negative* bacteria, but the opposite can not always be observed; in

particular, certain gene promoters allowing transcription are not recognised by the bacteria

which have captured the DNA fragments containing them.

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4. However…

4.1. Little is known about the adaptation potential of “lab creatures”

Although, through observations, it seems that model strains and strains modified in

laboratories have lost their capacity for adaptation and colonisation, this does not rule out the

possibility of a variant departing from this rule. For example, researchers have recently noted

the survival of genetically improved strains of Sinorhizobium meliloti in soils for six years,

even in the absence of the legumes with which they form a symbiotic relationship (Donegan

et al., 1999).

4.2. Gene transfers in nature are difficult to assess

The complex nature of the relationships between microbial populations within an ecosystem

makes it very difficult to assess the importance of gene flow between microorganisms, as well

as the nature and diversity of the genes involved. In-depth studies are necessary in order to

assess the importance of these transfers for the evolution of microorganisms as well as the

possibility that a recombinant microorganism might transfer its DNA to a microorganism that

occurs naturally in the environment. Recent studies have shown that genetically improved

strains of Sinorhizobium meliloti (Donegan et al., 1999) transferred DNA to endogenous flora

in the soil and that these transfers could be facilitated in the digestive tracts of arthropods

present in the soil.

4.3. Genetic engineering causes modifications which are not naturally possible

Even if mutations and therefore modifications of genes occur spontaneously in nature and

give new properties to microorganisms, some of the modifications carried out by humans are

not at all spontaneously possible in nature. This is the case, for example, in the production of

human hormones such as insulin using Escherichia coli, through the cloning of the human

gene in the bacteria. The probability of this spontaneously occurring by genetic mutation or

transfer in nature is practically zero.

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In the same way, due to the mechanisms which limit the transfers of genes of different sizes,

many genes cannot be exchanged between different species. Researchers, however, have the

possibility of lifting these barriers between species and allowing gene transfers which would

not naturally have been able to take place. Some researchers believe that, in so doing, the

combination of transgenic harvests and genetically modified biopesticides (such as

Agrobacterium radiobacter and Pseudomonas fluorescens) may create genetic

recombinations which are likely to have devastating effects on the microflora and microfauna

in soils.

5. Is it possible to avoid the use of genetically modified microorganisms?

5.1 Is the use of GMMs essential?

Microbial GMOs may potentially be used in the manufacture of recombinant molecules*

(drugs, intermediate products in the agri-food industry), the production of fermented

foodstuffs (alcoholic drinks, dairy products, etc.), pollution control (sewage, hydrocarbons),

the improvement of crop production by facilitating symbiosis between plants and

microorganisms (nitrogen fixation) and the substitution of various technologies

(biolixiviation, etc.).

The reasons which are leading to the use of GMMs, or which may do so in the future, may be

of an economic nature and/or may relate to the health of humans, animals or plant life. Every

time a GMM is used, it is imperative that the risks involved in its use be compared to those

which would exist if the GMM were not used.

In theory, in the case of molecules produced in fermenters, the GMM is not released into the

natural environment. In order to ensure that there are no leaks, fermentation plants must be

made more secure, therefore adding to the costs involved in the process. Nevertheless, this

process is controllable and therefore considerably reduces the risks involved in the use of

GMMs.

Some of the molecules produced in this way have enabled the treatment of conditions for

which the pharmaceutical alternatives were far from comparable and even represented a

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certain risk. For example, before it was produced using a recombinant E. coli strain, human

growth hormone was produced using hypophyses taken from human corpses. Some batches,

which were made from hypophyses contaminated with the agent responsible for Creutzfeldt-

Jakob disease, were responsible for the transmission of this disease to children being treated

for dwarfism with this hormone. Before recombinant insulin became commercially available,

diabetics were treated with modified pig insulin against which, after a certain length of time,

the human body produced antibodies.

In addition to these important advantages concerning the purity and quality of the molecule,

such cloning of microorganisms offers, due to the ease of production, the twofold benefit of a

considerable reduction in production costs, allowing more people to be treated, and the

possibility of carrying out research into new uses. For example, growth hormone now has

other applications (which are well-known in the field of competitive sport) over and above the

restoration of growth in children suffering from dwarfism.

As far as the manufacture of drugs is concerned, there seems to be no doubt that the use of

GMMs, insofar as they are not released into nature, represents progress for our society. On the

other hand, several other molecules are produced to essentially economic ends in order to

improve or stabilise a technological process. This is the case for many enzymes which are

used in food processing, such as amylases which are used in brewing, proteases used in the

meat industry and chymosin used during cheese production. There are often alternatives to the

use of these molecules: they may be naturally synthesised by a microorganism which does not

necessarily need to be a GMM (for example, Bacillus subtilis produces proteases) or they may

be extracted from another organism (chymosin may also be extracted from calf rennet, which

has traditionally been used for centuries in cheese-making technology). In the eyes of their

critics, the use of GMOs in the production of molecules may be seen to be questionable if

these can be produced by an alternative process. It must be borne in mind, however, that the

process in question — cultivation in fermenters — does not lead, in theory, to the release of

modified microorganisms into the environment. Moreover, the reduction in costs of a process

through the use of molecules derived from GMMs may allow more people to consume the

resulting food products.

If the risks involved in the use of fermenters seem to be controllable, the same can probably

be said for the majority of molecules derived from microbial GMOs: where they are identical

to naturally occurring molecules, the risks involved in their ingestion seem low. The

consumption of cheeses made with recombinant chymosin is thus common (something which

18

proved to be very useful during the BSE crisis in order to replace calf rennet, which was

likely to have been contaminated by the BSE agent).

As regards GMMs which are released or used in the environment, the risks involved in their

use are greater than in the above example as it is conceivable that they may disrupt

ecosystems, either because they may transfer their modified genes to another microorganism,

providing the latter with “colonising” properties, or because their development may be to the

detriment of endogenous species. This is why the use of modified strains in the manufacture

of fermented food products for commercial purposes is currently banned in Europe, following

the precautionary principle. The same is true for strains intended for use in pollution control

or to improve the growth or resistance of plants. Developments in cloning technologies, such

as the insertion of genes into the chromosome, may lead to a relaxation of legislation as has

been the case in other countries (the United States has just authorised the use of a modified

strain of Rhizobium meliloti in the environment) and to the authorisation of the use of

genetically modified strains in food products and in the environment.

As far as GMMs which are available for use in the production of fermented foodstuffs are

concerned, these essentially aim to improve production processes (the development of strains

of L. lactis which are resistant to bacteriophages for the production of cheeses is a good

example) or to improve the organoleptic, nutritional and hygienic properties of food. These

improvements may, however, be achieved using other means such as the selection of

appropriate non-modified strains or adherence to hygiene standards.

With regard to GMMs used in pollution control, the problem is more complex as the risks

involved in their dispersal into the environment — which is also a form of pollution — must

be compared with the risks of environmental pollution. In any case, it seems that even if

GMMs provide ad hoc solutions to such problems, the long-term aim must be sustainable

development and the prevention of pollution.

The issues surrounding GMMs which are used in conjunction or in symbiosis with plants are

more delicate. In this context, GMMs are used to improve plant productivity or to develop the

resistance of crops to harmful insects or pesticides. A solution which allows production costs

to be lowered or productivity to be improved, especially in areas where crop production is

difficult, cannot be immediately rejected out of hand. Even if alternative methods of

cultivation — such as those which avoid the use of polluting fertilizers or pesticides — or

sustainable development appear to be less effective than the development of techniques which

use GMMs, it becomes difficult to justify rejection of these techniques.

19

However, as noted above, the risks involved in the release of GMMs into the environment

must be assessed. As long as these risks are undefined, the precautionary principle, which

advises against the use of GMMs, remains valid.

The most complex issue relates to the use of live GMMs to treat certain human and animal

diseases. For example, species used in food production, such as Lactococcus lactis, have been

genetically modified in such a way as to secrete molecules through the mucosa (the digestive

membrane, for example) in order to treat medical conditions (Chang et al., 2003). This form

of treatment seems promising and should, in some cases, prove to be more effective than

traditional allopathic medicine. These strains are ingested and passed through the human

digestive tract and are therefore released, in living form, into the environment. This is why a

current line of research involves the development of strains which will not be able to survive

outside the digestive tract. In the meantime, however, if we compare the benefits they provide

with the potential risks posed to the environment, it seems difficult at the current time to

decide on whether these GMMs are absolutely necessary.

The final category, which concerns GMMs produced in laboratories, is by far the most

extensive in terms of the diversity of the experiments carried out and the strains obtained. The

cloning of microbial genes in model microorganisms such as E. coli, B. subtilis or L. lactis,

which is often necessary in order to obtain data on their regulation and expression, is a

procedure which is often very difficult to avoid. This is why the freezers of molecular biology

laboratories are often overflowing with genetically modified strains. An understanding of the

prokaryotic genome has often been a prerequisite for understanding more complex genomes

such as the human genome, which is why it seems impossible to consider the abandonment of

research using GMMs, insofar as the provisions set in place to avoid their dispersal into the

environment are carefully followed.

5.2. Are researchers able to evaluate the legitimacy of their work?

As we have seen, fundamental research on genomes and on the way in which organisms work

requires the use of genetic engineering, meaning that the development of GMOs in

laboratories does not always directly comply with sometimes arguable economic imperatives.

However, experience has taught us that these scientific advances also serve interests which go

against the well-being of humans and their environment. Nonetheless, it seems impossible to

20

determine beforehand the consequences linked to the acquisition of new scientific knowledge

which will be harmful to humankind.

It is indisputable that the acquisition of this fundamental knowledge is essential as it

subsequently leads to applied research which aims, in particular, to improve the conditions in

which humans live and to preserve their environment.

Nevertheless, researchers are entitled to call into question some lines of research which may

increase risks to the health of humans, animals or plant life or to the ecological balance of the

planet. The development of microbial strains with improved pathogenic capabilities in order

to expand the arsenal of biological weapons provides a clear illustration of this. Even though

it may appear difficult at first sight, every researcher has a responsibility to be concerned

about the potential consequences of his or her work.

The freedom of researchers as to the purpose of their research is, however, becoming hindered

to an ever greater extent by economic imperatives: in order to work, they need financial

assistance which is dependent on the scientific guidelines dictated by the State or on the needs

of businesses. If it can be said that the business community is directly motivated by economic

imperatives and pays relatively little attention to humanitarian considerations, this is not

necessarily true for the State. However, over the past few years in France, the State has tended

to withdraw from the field of research, thus strengthening the ties between businesses and

researchers.

6. Conclusion

Since the era of Pasteur, for practical reasons, the way in which microorganisms work has

been studied in vitro on pure strains under the conditions and in the environment of the

laboratory, thus revealing a mere fragment of the complexity of the microbial world. The

scientific community has been aware for some years of the need to study microorganisms in

their environment; however, the knowledge which is necessary to understand how microbial

ecosystems work is insufficient. It is therefore very difficult at the current time to predict the

influence that the dispersal of genetically modified microorganisms into our environment may

have. Several studies, in particular relating to gene transfer, will be necessary over the coming

years in order to give an accurate assessment of the risks and, consequently, to develop

GMMs which do not pose a risk to humans and their environment. Several GMM strains are

currently being used in conditions which limit this risk, such as production in fermenters. In

21

theory, the precautionary principle is applied in other cases, in particular in Europe, where

such uses must be approved by the relevant authorities. However, in view of the real technical

difficulties relating to the detection of these microorganisms, their unlawful use, in particular

by industrialists, is a cause for concern. As regards fundamental research on microorganisms

which gives rise to new modified strains or new technologies, the question of the real need for

such research must be considered in the same way as with all research in all disciplines.

GLOSSARY

Amino acids: Molecules that make up proteins

Cytoplasmic bridge: Link between the two bacterial cells

Enzyme: Protein substance that catalyses biochemical reactions. It is effective in minute

amounts and is not altered by the reaction

Eukaryotic: Organism whose chromosomes are confined to the nucleus

Gram-positive, Gram-negative: Two important bacterial groups that differ in cell wall

composition

Mutation: Genome alteration

Nucleic acid: DNA, RNA

Organoleptic: Affecting the sense organs

Phylogenetics: Branch of genetics that studies genetic changes in species through evolution

Recombinant molecules: Molecules whose gene was cloned into another organism (in this

case into a GMM)

Recombination: Gene rearrangement

22

Toxigenic: Produces one or more toxins

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